According to the US Census Bureau in 2007 there were approximately 112,400,000 households in America. Approximately fifty percent or 55,900,000 of those households were occupied by married couples. Approximately 62% of married families have both spouses in the workforce. Any tax policies that affect such a large percentage of the nation’s households are important public policy concerns. Marriage has a significant effect on taxation. A couple may experience a marriage penalty or benefit depending upon their earnings, credits and deductions. For the purposes of this article the marriage penalty or benefit is defined as the difference in federal tax liability between what a married couple would pay and what two single persons would pay (Beach & Herderman). In this paper we present a conceptual model and detailed list of the tax code items that result in marriage penalty or benefit. We then discuss the implications of tax policies that reward some marriages while penalizing others.